2003 Tahoe coolant system leak or head gasket leak?

[tomloans]

Alright! Yet another coolant loss post. I have completely replaced the cooling system and I mean everything. Started losing fluid again shortly after. Put 20PSI pressure on the system and found a leak at one of the new tees at the firewall and the hose at the water pump. Tightened hose and fiddled with the T. Those leaks are stopped. Still losing coolant somewhere and there is air in the system when I do. Here is the symptoms...

Yesterday for instance, I was driving in the city and the low coolant warning light came on for a few seconds. When I came home, I killed the engine and came out a little later and the level was perfect. This morning when I started it, it suck in so much coolant that it almost emptied the tank. I had about an inch of coolant left in the tank. What does this mean?

I guess the question is, is there a proven method to see if the engine is sucking in coolant and burning it? This is quite frustrating as I systematically replaced everything and kind of tired of adding coolant every 100 miles or so.

 

[wjburken]

Does your exhaust smell like coolant?

What does your oil look like?

 

[tomloans]

Does your exhaust smell like coolant?

What does your oil look like?

No it doesn't smell and the oil is perfect. But maybe it is a slow leak into the combustion system and so I can't smell it yet until it leaks worse? I actually just ran out there and put the pressure test again on it. 20 psi and there is zero leaks anywhere. But I was losing pressure slowly. Got down to about 17 PSI in about 5 minutes or so. But it is hard to say if my cheap pressure tester is leaking or something in the engine. Usually with this test, I quickly see the leak as it will start dripping from the leak location. I have absolutely nothing leaking anywhere. Soooooooo... Head gasket!? This is really frustrating. The vehicle is perfect otherwise. Runs like new and I have 205k miles on it. I have taken extreme care of this car since new when I bought it back in 2003.

 

[iamdub]

No it doesn't smell and the oil is perfect. But maybe it is a slow leak into the combustion system and so I can't smell it yet until it leaks worse? I actually just ran out there and put the pressure test again on it. 20 psi and there is zero leaks anywhere. But I was losing pressure slowly. Got down to about 17 PSI in about 5 minutes or so. But it is hard to say if my cheap pressure tester is leaking or something in the engine. Usually with this test, I quickly see the leak as it will start dripping from the leak location. I have absolutely nothing leaking anywhere. Soooooooo... Head gasket!? This is really frustrating. The vehicle is perfect otherwise. Runs like new and I have 205k miles on it. I have taken extreme care of this car since new when I bought it back in 2003.

Might need to look under the rocker covers for evidence of a cracked head. Some leaks are worse with the engine hot and almost non-existent when cool.

How long, time and/or mileage, has this been going on?

 

[tomloans]

Might need to look under the rocker covers for evidence of a cracked head. Some leaks are worse with the engine hot and almost non-existent when cool.

How long, time and/or mileage, has this been going on?

It has been going on for about 10k miles and a good 3 years or so but frankly I am not sure. I decided since everything was quite old and some items were mostly original, I decided to just take care of the entire system at once including water pump and radiator and everything on the list with the exception of the pipes running to the back of the car for the rear seat heating system. (these cars are so easy to work on!). Do you think there may be a leak in rear heating system? ( but there was no drips there either with 20 PSI )

 

[iamdub]

It has been going on for about 10k miles and a good 3 years or so but frankly I am not sure. I decided since everything was quite old and some items were mostly original, I decided to just take care of the entire system at once including water pump and radiator and everything on the list with the exception of the pipes running to the back of the car for the rear seat heating system. (these cars are so easy to work on!). Do you think there may be a leak in rear heating system? ( but there was no drips there either with 20 PSI )

Ah. So, it's not just air purging from the system after being opened up to replace a bunch of parts.

Your symptoms are very much like what my brother's truck experienced and we found he had the common Castech head failure. Slow, but persistent coolant loss, no milkshake in the oil and no external leaks. He lost oil pressure one day and when I removed the driver side rocker cover, I saw the telltale sign of coolant intrusion as well as the crack around the head bolt hole. It was a small enough leak to not make a milkshake of the oil since the water in the coolant could steam off while driving. The remaining coolant residues in the oil caused the whole inside of the engine to be sludged up. A large chunk of sludge broke free and was sucked up by the oil pickup, blocking the oil flow to the pump.

Pop off a rocker cover. I suggest the driver side since it's easier to access. It's about a 30-minute job taking your time.

 

[tomloans]

Shoot I just replaced the cover with the updated cover! Didn't know to look. LOL Yes it was very easy to do. I will do that asap. Hate to have the oil pump clogged. Really appreciate your feedback. Where can I get a good rebuilt Cylinder head. Seems like a lot outfits out there doing this work. Where would you suggest I get one. Maybe I should purchase new?

 

[89Suburban]

Throw some alumaseal powder in it and see what happens. I would think a cracked head would show signs on a spark plug inspection?

 

[iamdub]

Shoot I just replaced the cover with the updated cover! Didn't know to look. LOL Yes it was very easy to do. I will do that asap. Hate to have the oil pump clogged. Really appreciate your feedback. Where can I get a good rebuilt Cylinder head. Seems like a lot outfits out there doing this work. Where would you suggest I get one. Maybe I should purchase new?

His was really bad as it had been going on for a long time. He had only owned the truck for maybe a year, if even that. I wouldn't be surprised if that was why the previous owner got rid of it. Under the cover and all inside the engine was thick and black gunk. You would've noticed that had yours been that bad. If yours is cracked, it could be somewhat recent and you can easily save it.

At the time, we couldn't find any known good heads. We figured our safest bet would be to track down non-Castech 706s but we found none. We ended up putting some low-mileage 799s from a 2010 5.3 on it. He lost a little compression with them. But, they were cheap and it's just his camp truck. I couldn't steer you towards any particular source for a rebuilt head. In my mind, they're all a risk. So, find someone reputable that is very much aware of such a failure and warranties their product. IIRC, a member here bought a head (or set of heads) from a rebuilder and one was cracked. The Castech failure mostly happens around the head bolt holes and doesn't show unless the head is installed/torqued down.

 

[Bill 1960]

Use a combustion gas tester on the cooling system. Only costs about $50.